In a manufacturing process of an electronic device such as a semiconductor device, a liquid crystal display device or the like, an etching process for etching a film on a substrate in a predetermined shape is carried out to form a predetermined circuit pattern on the substrate.
In the aforementioned etching process, a plasma etching process is widely used. A plasma etching apparatus has, e.g., in a processing chamber thereof, a lower electrode for mounting a substrate thereon, and a shower head, also serving as an upper electrode, for injecting a predetermined gas toward the substrate on the lower electrode. The etching process is performed to etch a film on the substrate in such a manner that a high frequency power is applied between the upper and the lower electrode to produce a plasma in the processing chamber, e.g., while a predetermined gaseous mixture is being injected into the processing chamber through the shower head.
However, in case where the gaseous mixture is supplied into the processing chamber through the shower head to perform the etching process on the substrate, as mentioned above, there was a problem that etching characteristics such as etching rate, etching selectivity, etching shape and the like at the central portion of the substrate are different from those at the outer peripheral portion of the substrate, respectively. This has been attributed to the fact that, in the processing chamber, a concentration and a component of the gaseous mixture at the central portion of the substrate are different from those at the outer peripheral portion of the substrate, respectively. Therefore, e.g., in Japanese Patent Laid-open Application No. H08-158072, there has been proposed that an inside of an upper electrode as a shower head is divided into a plurality of gas chambers; gas introducing lines are independently connected to the respective gas chambers; and the gaseous mixtures of specified mixing ratios and flow rates are supplied to the central portion and the outer peripheral portion of the substrate, respectively. In this way, it is possible to improve an in-substrate uniformity, e.g., in the etching rate, by respectively adjusting mixing ratios and flow rates of the gaseous mixtures supplied to the central portion and the outer peripheral portion of the substrate in the processing chamber.
Meanwhile, in the case mentioned above, to set the respective mixing ratios and flow rates of the gaseous mixtures supplied to the central portion and the outer peripheral portion of the substrate, all etching characteristics such as etching rate, etching selectivity and etching shape need to be considered, and then, setting of each gaseous mixture is carried out such that each etching characteristic of in-substrate becomes uniform. Since, however, a relationship between each etching characteristic and the mixing ratio or the flow rate of each gaseous mixture supplied to the central portion or the outer peripheral portion of the substrate was not clearly defined, it was difficult to properly perform the setting of each gaseous mixture. Further, it takes much time to find the proper setting of each gaseous mixture and fix it.